A description of some technologies related to embodiments of the invention follows:
U.S. Pat. No. 4,662,004 Fredriksen, et al. Fredriksen describes an optical communication link that includes a separate laser (in addition to the data transmission laser), which returns information about the level of the received signal to the transmitter. This separate laser is adjusted to emit power proportional to the received beam power.
U.S. Pat. No. 4,832,402 Brooks. Brooks describes a fast scanning mirror used to time-multiplex light beam into several steering mirrors, in which each of the steering mirrors aim the beam into one or a group of targets clustered together. The steering mirrors are slow due to the large angle required. Brooks also describes the use of “beacon transmitters” to said in target tracking (column 9 line 15).
U.S. Pat. No. 5,282,073 Defour, et al. Detour shows optical communications system with two galvanometer mirrors for beam steering, and a complex wide-angle lens to increase the angular scanning to a half-sphere. Defour also describes a target designation step, an iterative step of bilateral acquisition and a third step of exchanging data.
U.S. Pat. No. 5,390,040 Mayeux. Mayeux describes the use of one steerable mirror at the expanded beam location for aiming both the transmit beam and receive beam. Part of the surface of the mirror is used for transmission, and another part is used for reception. (Mayeux calls these parts of the mirror “field of views”, in contrast to common terminology.)
U.S. Pat. No. 5,448,391 Iriama, et at. Iriama describes the use of an optical Position Detector sensor (common art) to track the beam direction. A pair of mirrors is used for slow, large angle direction control and a fast lens is moved for fast corrections.
U.S. Pat. No. 5,646,761 Medved, et at. Medved describes an optical communications between a stationary location, like an airport gate, and a movable object, like an airplane parked at the gate. The optical units on the gate and the airplane are searching for each other, and stop this search when aligned.
U.S. Pat. No. 5,710,652 Bloom, et at. Bloom describes optical transmission equipment to interconnect low Earth orbit satellites. The whole transmitter and receiver unit is mounted on gimbals. Two lasers are used, one for tracking and one for data. A CCD optical detector detects a target location for tracking a servo control.
U.S. Pat. No. 5,768,923 Doucet, et al. Doucet discloses the distribution of television signals from one source to many receivers. The transmitter uses an X-Y beam deflector made of two galvanometer driven mirrors. This assembly is used to direct the beam into a specific receiver at a selected home.
U.S. Pat. No. 5,818,619 Medved, et al. Medved describes a communications network with air-links. A converter unit is converting the physical data transmission in the network to electricity, and drives an air-link transmitter. Similarly, the received beam is converted to electricity after reception. Medved also describes an optical switch to have one air-link serving plurality of networks between the same two locations.
EP 962796A2 Application Laor, et al. This application describes MEMS mirror construction.